Method for data flow control in a mobile communications system

ABSTRACT

The invention relates to a method for controlling the flow of data between an RNC (R) and a base station (BS) of a UMTS mobile communications system with HSDPA capability via an lub interface (I 2 ), where an HS-DSCH Frame Protocol mechanism is implemented in the lub interface (I 2 ) to provide control and data services for the communication of HSDPA user data between the RNC and the base station, wherein a capacity overload control entity (COCU) monitors information about actual lub interface data transport flow (IDF), and when a determined lub interface (I 2 ) transport capacity value is reached, the data transport flow is reduced in the lub interface (I 2 ).

This is a divisional of application Ser. No. 11/191,996 filed Jul. 29,2005. The entire disclosure of the prior application, application Ser.No. 11/191,996 is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention is based on a priority application EP 04292052.0 which ishereby incorporated by reference

The present invention relates to wireless communication systems, andmore particularly, to data flow control in a mobile communicationssystem.

The third generation (3G) evolution of Global Systems for Mobilecommunications (GSM) networks, commonly known as Universal MobileTelecommunications Systems (UMTS), introduces High Speed Downlink PacketAccess (HSDPA) to provide data rates up to approximately 10 Mbps tosupport packet-based multimedia services.

UMTS HSDPA capable systems support an additional transport channel typein the downlink direction, a High Speed Downlink Shared Channel(HS-DSCH). This logical channel provides the logical transport mechanismfor data transfer.

Currently the 3rd Generation Partnership Project (3GPP) is undertakingthe technical specification of HSDPA. 3GPP specification TS 25.435v5.6.0, 2003-12, provides a description of the interface between a radionetwork controller (RNC) and a base station, being referred to as thelub interface. In such document, and more specifically, in chapter5.1.6, a data transfer procedure is defined for the transmission ofHS-DSCH data frames from the RNC to the base station. A mechanism tocontrol user data flow between the RNC and the base station is alsoimplicit in such procedure.

Since the actual transport capacity on the lub interface is limited, dueto the fact that the base station will be connected to the RNC via oneor several physical communication links, such as 2.048 Mbps (E1) linksor 155 Mbps (STM-1) links, a disadvantage of the specified state of theart RNC-base station user data flow control approach is that it onlycontrols individual user data flows, that is, how much HSDPA traffic anindividual user can receive from the RNC. Based on the distribution ofthe user terminals and the quality of the air interface for a radio cellwith HSDPA traffic and in case, for example, the base station needs toserve several of such cells, there is the probability that the totaldata transport flow in the lub interface, that is the sum of allindividual user data flow instances, exceeds the maximum available lubinterface transport capacity, i.e. a capacity overload situation occursat the lub interface.

SUMMARY OF THE INVENTION

It is the object of the invention to solve the aforesaid technicalproblems and provide an improved data flow control method for the lubinterface between the RNC and the base station.

The object is achieved by a method for controlling the flow of databetween an RNC and a base station of a UMTS mobile communications systemwith HSDPA capability via an lub interface, where an HS-DSCH FrameProtocol mechanism is implemented in the lub interface to providecontrol and data services for the communication of HSDPA user databetween the RNC and the base station, the method comprising the stepsof:

-   -   sending an HS-DSCH Capacity Request control message from the RNC        towards the base station indicating a total amount of user data        waiting in the RNC, in order to request data transport capacity,    -   sending an HS-DSCH Capacity Allocation control message from the        base station towards the RNC granting the amount of data the RNC        is allowed to send within a period of time,    -   the RNC sending the granted amount of user data information to        the base station by means of an HS-DSCH Data Frame message,    -   a capacity overload control entity monitoring information about        actual total lub interface data transport flow, and when a        determined lub interface transport capacity value is reached,        reducing the data transport flow in the lub interface.

The object is also achieved by a capacity overload control entity of aUMTS mobile communication system with HSDPA capability comprising meansfor detecting and/or calculating and/or receiving information aboutactual lub interface data transport flow; means for analyzing saidinformation and determining if it has reached a certain threshold value;means for communicating with a radio network controller and means forsending to the radio network controller information about the actual lubinterface data transport flow or an indication that the actual total lubinterface data transport flow has reached a certain lub interfacetransport capacity value;

-   -   a radio network controller of a UMTS mobile communication system        with HSDPA capability comprising means for communicating with a        base station via an lub interface by means of an HS-DSCH Frame        Protocol mechanism; means for detecting and/or calculating        and/or receiving and/or sending information about actual lub        interface data transport flow; means for analyzing said        information and determining if a certain lub interface transport        capacity value has been reached or for receiving an indication        that the actual total lub interface data transport flow has        reached a certain lub interface transport capacity value; means        for sending a capacity threshold indication in an HS-DSCH frame        protocol message to the base station or means for transmitting        to the base station an amount of user data which is less than a        previously allocated amount of data granted by that base        station;    -   and a base station of a UMTS mobile communication system with        HSDPA capability comprising means for communicating with a RNC        via an lub interface by means of an HS-DSCH Frame Protocol        mechanism; means for receiving a capacity threshold indication;        means to analyze said capacity threshold indication and to react        to it by sending an HS-DSCH Capacity Allocation control message        towards the RNC reducing the amount of data the RNC is allowed        to send within a period of time.

Advantageous configurations of the invention emerge from the dependentclaims, the following description and the drawings. For example, it isseen advantageous that, by using the proposed invention, efficient usageof the transport capacity on the lub interface for HSDPA traffic isachieved. It is also seen advantageous that the lub interface data flowcontrol method hereinafter described is used for a selective group ofusers thus providing the mobile network operator with a way ofdifferentiating the user quality of service and charge for such serviceaccordingly.

Furthermore, the invention provides an overall data flow control forHSDPA traffic on the lub interface.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment example of the invention is now explained with the aid ofFIGS. 1 to 4.

FIG. 1 shows a simplified basic network element architecture of aconventional mobile communication system.

FIG. 2 shows a simplified block diagram being illustrative of thecommunication between RNC, base station and user terminal in aconventional UMTS HSDPA mobile communication system.

FIG. 3 shows a block diagram being illustrative of a conventional datatransfer procedure for the transmission of HS-DSCH Data Frames from RNCto base station.

FIG. 4 shows a block diagram being illustrative of a method forcontrolling the flow of data between an RNC and a base station of amobile communications system with HSDPA capability according to theinvention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a basic network element architecture of aconventional mobile communication system comprising a core network CNconnected via interface I3 to a radio access network RAN whichcommunicates via an air interface I1 with eight user terminals T1 to T8.The radio access network RAN comprises four base stations BS1 to BS4controlled by two radio network controllers R1 and R2. The RNCs R1 andR2 are connected among themselves via interface I4 and are connected tothe base stations via the lub interface I2. The lub interface I2 and theother network element interfaces I1, I3, I4 are also being specified by3GPP. In such specifications it is also common that the terminals arereferred to as user equipment (UE) and the base stations as Node Bs.

FIG. 2 shows an embodiment where the RNC R transfers user data UD bymeans of HS-DSCH Data Frames HDT to a base station BS via the lubinterface I2 and the base station transmits said user data to the userterminal T.

In operation, the RNC receives user data UD, e.g. multimedia data suchas video sequence, from the core network. User data UD is segmented inthe RNC R in a

Medium Access Control (MAC) protocol entity MU1 to provide MAC datapackets, which are also referred to as MAC-d protocol data units (PDUs).Said MAC-d PDUs in the RNC are passed to an HS-DSCH frame protocolentity HFPU1 responsible for the HSDPA lub Interface communicationbetween the RNC R and the base station BS. User data in form of MAC-dPDUs is then transferred to the base station BS in an HS-DSCH Data FrameHDT by using the control and data services of the HS-DSCH frame protocolentity HFPU1 and HFPU2.

Once received in the base station BS, the HS-DSCH frame protocol entityHFPU2 passes the user data MAC-d PDUs to MAC protocol entity MU2 whichconcatenates several of such MAC-d PDUs to form MAC-hs PDUs which aretransmitted to the HSDPA capable user terminal T.

In FIG. 3 it is illustrated with more detail the HSDPA lub interface I2HS-DSCH frame protocol service for the transmission of HS-DSCH DataFrames HDT from RNC R to base station BS.

An HS-DSCH Capacity Request procedure provides means for the RNC R torequest HS-DSCH capacity, that is, the reception of data packets in theRNC is signalled towards the base station BS by means of a HS-DSCHCapacity Request control message HCR, which includes the total amount ofdata waiting, i.e. user buffer size, in the RNC.

The base station BS will grant transport resources to the RNC by meansof a HS-DSCH Capacity Allocation control message HCA, which defines theamount of data, i.e. size and number of MAC-d PDUs, the RNC is allowedto send within a defined time period. The base station BS may generatean HS-DSCH Capacity Allocation control message HCA either in response toan HS-DSCH Capacity Request or at any other time, and the base stationBS may use this message to control individual user data flow and modifythe capacity at any time, irrespective of the reported user bufferstatus.

Based on the granted transfer capacity by the base station, the RNCproceeds by sending user data in HS-DSCH Data Frames HDTs to the basestation. Each HS-DSCH Data Frame includes besides the MAC-d PDUs also anindication about the remaining user data, i.e. buffer size in the RNC,which might be used by the base station for the issue of a new HS-DSCHCapacity Allocation control message HCA.

FIG. 4 shows an embodiment illustrating a method for data flow controlbetween an RNC R and a base station BS according to the invention. Theembodiment of FIG. 4 shows a UMTS mobile communications system withHSDPA capability comprising network elements RNC, base station andcapacity overload control entity COCU according to the invention. Thecapacity overload control entity COCU is connected to RNC R, and the RNCis connected to base station BS via lub interface I2.

The capacity overload control entity COCU according to the invention isdesigned so that it monitors information about actual lub interface datatransport flow IDF, that is, for example, it has means to detect and/orcalculate and/or receive information about dedicated channel (DCH)traffic, HSDPA traffic, control traffic and total lub interface capacityavailable for data transport towards a base station BS. The capacityoverload control entity COCU is further designed so that when adetermined lub interface transport capacity value is reached itgenerates a capacity threshold indication CI and sends it to the RNC.

Upon reception of the capacity threshold indication CI from the capacityoverload control entity COCU, and according to the invention, the RNCsends said capacity threshold indication CI in an HS-DSCH frame protocolmessage to the base station, and the base station reacts to said messageby sending an HS-DSCH capacity allocation control message towards theRNC reducing the amount of data the RNC is allowed to send within aperiod of time.

The lub interface I2 transport capacity value can be determined forexample to a certain percentage value below the maximum transportcapacity of the lub interface I2 or set to the maximum transportcapacity of that lub interface. In the first case, when that value isreached, the capacity overload control entity COCU sends to the RNC acapacity threshold indication CI that a critical load situation occurs,and in the second case the capacity overload control entity COCU sendsto the RNC a capacity threshold indication CI that an overload situationoccurs. In case, for example, that the capacity overload control entityCOCU indicates to the RNC an overload situation and this indication istransferred to the base station, the base station can reduce the amountof data the RNC is allowed to send to a value of zero.

For sending the capacity threshold indication CI to the base station,the RNC can use for example an HS-DSCH Data Frame message and code thespecific capacity threshold indication CI in a determined bit field ofsuch message. But it is also possible that the RNC uses another HS-DSCHframe protocol message.

It is also possible that the capacity overload control entity COCU sendsto the RNC at certain periods of time current lub interface I2 transportcapacity or data transport flow information so that the RNC can reactand take decisions based on this information.

An alternative way, according to the invention, of indicating to thebase station that a certain lub interface I2 transport capacity valuehas been reached, can be done the following way: upon reception of thecapacity threshold indication CI from the capacity overload controlentity COCU, the RNC transmits to the base station an amount of userdata which is less than the previously allocated amount of data grantedby that base station. The base station reacts to said behavior from theRNC by sending an HS-DSCH Capacity Allocation control message towardsthe RNC reducing the amount of data the RNC is allowed to send within aperiod of time. For example, in case the capacity overload controlentity COCU generates a capacity threshold indication CI indicating anlub interface overload situation, the RNC can react by sending to thebase station an HS-DSCH Data Frame message with no user data inside,thus the base station recognizes the meaning of this RNC behavior andinterprets it as an overload situation. The base station in this casecan react by generating a HS-DSCH Capacity Allocation control messagetowards the RNC reducing the amount of data the RNC is allowed to sendwithin a period of time to zero.

As already mentioned above, it is seen advantageous that by using thedata flow control method according to the invention the operator of themobile communications network can avoid lub interface overloadsituations and provide a more reliable and efficient data user transportservice between the radio network controller and the base stations.Furthermore, when a determined load situation is reached in the lubinterface, the operator can reduce the data transport flow for adetermined number of users based on low priority of data or low qualityservice offered to such users, thus allowing the other high qualityservice customers to keep receiving data without being affected by anoverload situation.

In a preferred embodiment of the invention the capacity overload controlentity COCU is located within the RNC, said capacity overload controlentity being implemented in a hardware and/or software form, but it canalso be located in another network element of the mobile communicationssystem or as a standalone entity in such network systems.

For the sake of generalization, it shall also be understood that meansto carry out the method or certain steps of the method for controllingthe flow of data between an RNC and a base station of a UMTS mobilecommunications system with HSDPA capability herein described can belocated anywhere in the mobile communications system, that is, in a basestation or any resource manager entity of the mobile communicationsystem. Said means being implemented in hardware or software form.

1. A capacity overload control method of a Universal MobileTelecommunications Systems (UMTS) mobile communication system with HighSpeed Downlink Packet Access (HSDPA) capability comprising: determininginformation about actual Iub interface data transport flow based ondedicated channel traffic, HSDPA traffic, and control traffic; analyzingthe information about the actual Iub interface data transport flow anddetermining if the actual Iub interface data transport flow has reachedan Iub interface transport capacity value; and communicating with aradio network controller and sending to the radio network controller theinformation about the actual Iub interface data transport flow or anindication that the actual Iub interface data transport flow has reachedthe Iub interface transport capacity value, wherein the Iub interfacecomprises at least one physical communication link.
 2. The capacityoverload control method of claim 1, wherein the Iub interface transportcapacity value is set to a percentage of a maximum transport capacity ofthe Iub interface.
 3. The capacity overload control method of claim 1,wherein the Iub interface transport capacity value is set to a maximumtransport capacity of the Iub interface.
 4. A capacity overload controlentity method of a radio network controller (RNC) of a Universal MobileTelecommunications Systems (UMTS) mobile communication system with HighSpeed Downlink Packet Access (HSDPA) capability comprising:communicating with a base station via an Iub interface which comprisesat least one physical communication link, using a High Speed DownlinkShared Channel (HS-DSCH) Frame Protocol mechanism; determininginformation about actual Iub interface data transport flow based ondedicated channel traffic, HSDPA traffic, and control traffic; analyzingthe information about the actual Iub interface data transport flow anddetermining if an Iub interface transport capacity value has beenreached or receiving an indication that the actual Iub interface datatransport flow has reached the Iub interface transport capacity value;sending a capacity threshold indication in an HS-DSCH frame protocolmessage to the base station or transmitting to the base station anamount of user data which is less than a previously allocated amount ofdata granted by the base station; and receiving an HS-DSCH capacityallocation control message from the base station which reduces an amountof data the RNC is allowed to send to the base station within a periodof time.
 5. The capacity overload control method of claim 4, wherein theIub interface transport capacity value is set to a percentage of amaximum transport capacity of the Iub interface.
 6. The capacityoverload control method of claim 4, wherein the Iub interface transportcapacity value is set to a maximum transport capacity of the Iubinterface.
 7. The capacity overload control method of claim 4, furthercomprising receiving from the base station an HS-DSCH capacityallocation control message which reduces an amount of data the radionetwork controller is allowed to send to the base station within aperiod of time
 8. A capacity overload control entity method of a basestation of a Universal Mobile Telecommunications Systems (UMTS) mobilecommunication system with High Speed Downlink Packet Access (HSDPA)capability comprising: communicating with a radio network controller(RNC) via an Iub interface which comprises at least one physicalcommunication link, using a High Speed Downlink Shared Channel (HS-DSCH)Frame Protocol mechanism; receiving a capacity threshold indication fromthe RNC in an HS-DSCH frame protocol message; and analyzing the capacitythreshold indication and, in response to the capacity thresholdindication, sending an HS-DSCH capacity allocation control message tothe RNC which reduces an amount of data the RNC is allowed to send tothe base station within a period of time.
 9. A capacity overload controlmethod of a base station of a Universal Mobile TelecommunicationsSystems (UMTS) mobile communication system with High Speed DownlinkPacket Access (HSDPA) capability comprising: communicating with a radionetwork controller (RNC) via an Iub interface which comprises at leastone physical communication link, using a High Speed Downlink SharedChannel (HS-DSCH) Frame Protocol mechanism; detecting if the RNCtransmits to the base station an amount of data which is less than apreviously allocated amount of data granted by the base station; and inresponse to the detecting that the RNC transmits to the base station theamount of data which is less than the previously allocated amount ofdata, sending an HS-DSCH capacity allocation control message to the RNCwhich reduces an amount of data the RNC is allowed to send to the basestation within a period of time.
 10. A capacity overload control methodof a radio network controller (RNC) of a Universal MobileTelecommunications Systems (UMTS) mobile communication system with HighSpeed Downlink Packet Access (HSDPA) capability comprising:communicating with a base station via an Iub interface which comprisesat least one physical communication link, using a High Speed DownlinkShared Channel (HS-DSCH) Frame Protocol mechanism; sending a message tothe base station indicating a total amount of user data waiting in theRNC; receiving a message from the base station granting an amount ofuser data the RNC is allowed to send within a period of time; sendingthe granted amount of user data to the base station; determininginformation about actual Iub interface data transport flow; analyzingthe information about the actual Iub interface data transport flow anddetermines if an Iub interface transport capacity value has been reachedor receives an indication that the actual Iub interface data transportflow has reached the Iub interface transport capacity value; and sendinga capacity threshold indication in an HS-DSCH frame protocol message tothe base station or that transmits to the base station an amount of userdata which is less than a previously allocated amount of data granted bythe base station.
 11. A capacity overload control method of a basestation of a Universal Mobile Telecommunications Systems (UMTS) mobilecommunication system with High Speed Downlink Packet Access (HSDPA)capability comprising: communicating with a radio network controller(RNC) via an Iub interface which comprises at least one physicalcommunication link, using a High Speed Downlink Shared Channel (HS-DSCH)Frame Protocol mechanism; receiving a message from the RNC indicating atotal amount of user data waiting in the RNC; sending a message to theRNC granting an amount of user data the RNC is allowed to send within aperiod of time; receiving the granted amount of user data from the RNC;receiving a capacity threshold indication from the RNC; and analyzingthe capacity threshold indication and, in response to the capacitythreshold indication, sending an HS-DSCH capacity allocation controlmessage to the RNC which reduces an amount of data the RNC is allowed tosend to the base station within a period of time.
 12. A capacityoverload control entity of a Universal Mobile Telecommunications Systems(UMTS) mobile communication system with High Speed Downlink PacketAccess (HSDPA) capability comprising: a processor executing softwaremodules; a memory storing the software modules, wherein the softwaremodules comprise: a module to determine information about actual Iubinterface data transport flow based on dedicated channel traffic, HSDPAtraffic, and control traffic; a module to analyze the information aboutthe actual Iub interface data transport flow and determines if theactual Iub interface data transport flow has reached an Iub interfacetransport capacity value; and a module to communicate with a radionetwork controller and to send to the radio network controller theinformation about the actual Iub interface data transport flow or anindication that the actual Iub interface data transport flow has reachedthe Iub interface transport capacity value, wherein the Iub interfacecomprises at least one physical communication link.
 13. A radio networkcontroller (RNC) of a Universal Moblie Telecommunications Systems (UMTS)mobile communication system with High Speed Downlink Packet Access(HSDPA) capability comprising: a processor operable to execute softwaremodules stored in a memory; wherein the software modules comprise: amodule to communicate with a base station via an Iub interface whichcomprises at least one physical communication link, using a High SpeedDownlink Shared Channel (HS-DSCH) Frame Protocol mechanism; a module todetermine information about actual Iub interface data transport flowbased on dedicated channel traffic, HSDPA traffic, and control traffic;a module to analyze the information about the actual Iub interface datatransport flow and determines if an Iub interface transport capacityvalue has been reached or receives an indication that the actual Iubinterface data transport flow has reached the Iub interface transportcapacity value; a module to send a capacity threshold indication in anHS-DSCH frame protocol message to the base station or that transmits tothe base station an amount of user data which is less than a previouslyallocated amount of data granted by the base station; and a module toreceive an HS-DSCH capacity allocation control message from the basestation which reduces an amount of data the RNC is allowed to send tothe base station within a period of time.
 14. A base station of aUniversal Mobile Telecommunications Systems (UMTS) mobile communicationsystem with High Speed Downlink Packet Access (HSDPA) capabilitycomprising: a processor executing software modules; a memory storing thesoftware modules, wherein the software modules comprise: a module tocommunicate with a radio network controller (RNC) via an Iub interfacewhich comprises at least one physical communication link, using a HighSpeed Downlink Shared Channel (HS-DSCH) Frame Protocol mechanism; amodule to receive a capacity threshold indication from the RNC in anHS-DSCH frame protocol message; and a module to analyze the capacitythreshold indication and, in response to the capacity thresholdindication, sends an HS-DSCH capacity allocation control message to theRNC which reduces an amount of data the RNC is allowed to send to thebase station within a period of time.
 15. A base station of a UniversalMobile Telecommunications Systems (UMTS) mobile communication systemwith High Speed Downlink Packet Access (HSDPA) capability comprising: aprocessor executing software modules; a memory storing the softwaremodules, wherein the software modules comprise: a module to communicatewith a radio network controller (RNC) via an Iub interface whichcomprises at least one physical communication link, using a High SpeedDownlink Shared Channel (HS-DSCH) Frame Protocol mechanism; a module todetect if the RNC transmits to the base station an amount of data whichis less than a previously allocated amount of data granted by the basestation; and a module to send, in response to the detecting that the RNCtransmits to the base station the amount of data which is less than thepreviously allocated amount of data, an HS-DSCH capacity allocationcontrol message to the RNC which reduces an amount of data the RNC isallowed to send to the base station within a period of time.
 16. A radionetwork controller (RNC) of a Universal Mobile TelecommunicationsSystems (UMTS) mobile communication system with High Speed DownlinkPacket Access (HSDPA) capability comprising: a processor executingsoftware modules; a memory storing the software modules, wherein thesoftware modules comprise: a module to communicate with a base stationvia an Iub interface which comprises at least one physical communicationlink, using a High Speed Downlink Shared Channel (HS-DSCH) FrameProtocol mechanism; a module to send a message to the base stationindicating a total amount of user data waiting in the RNC; a module toreceive a message from the base station granting an amount of user datathe RNC is allowed to send within a period of time; a module to send thegranted amount of user data to the base station; a module to determineinformation about actual Iub interface data transport flow; a module toanalyze the information about the actual Iub interface data transportflow and to determine if an Iub interface transport capacity value hasbeen reached or receives an indication that the actual Iub interfacedata transport flow has reached the Iub interface transport capacityvalue; and a module to send a capacity threshold indication in anHS-DSCH frame protocol message to the base station or that transmits tothe base station an amount of user data which is less than a previouslyallocated amount of data granted by the base station.
 17. A base stationof a Universal Mobile Telecommunications Systems (UMTS) mobilecommunication system with High Speed Downlink Packet Access (HSDPA)capability comprising: a processor executing software modules; a memorystoring the software modules, wherein the software modules comprise: amodule to communicate with a radio network controller (RNC) via an Iubinterface which comprises at least one physical communication link,using a High Speed Downlink Shared Channel (HS-DSCH) Frame Protocolmechanism; a module to receive a message from the RNC indicating a totalamount of user data waiting in the RNC; a module to send a message tothe RNC granting an amount of user data the RNC is allowed to sendwithin a period of time; a module to receive the granted amount of userdata from the RNC; a module to receive a capacity threshold indicationfrom the RNC; and a module to analyze the capacity threshold indicationand, in response to the capacity threshold indication, sends an HS-DSCHcapacity allocation control message to the RNC which reduces an amountof data the RNC is allowed to send to the base station within a periodof time.